Method for Treating Heavy Fuel Oil

ABSTRACT

A method for on-ship processing of heavy oil which is to be utilized as fuel is disclosed. In an embodiment, the method includes providing the heavy oil for processing. The heavy oil is passed using a pump into a centrifuge with heating of the heavy oil, at least intermittently or permanently, to a separation temperature of more than 98° C. before the heavy oil reaches the centrifuge. An aqueous phase and a sludge phase are separated from a clean oil phase in the centrifuge.

The present invention relates to a method for on-ship processing ofheavy oil, for use as a fuel, especially for a diesel engine.

According to the online encyclopedia WIKIPEDIA and in the context ofthis application, a “heavy oil” (heavy fuel oil, HFO) is a residue oilfrom distillation or from cracking plants in mineral oil processing, andserves as a fuel for large diesel engines, as used, for example, onships and for steam locomotives with oil firing or in power plants forpower generation. The international trade designation of such an oil is:marine (residual) fuel oil (MFO); the US term Bunker C is sometimes alsoused.

It is known that heavy oils—especially in order to comply with ISO8217—before being combusted in diesel engines or in other units, can beprocessed directly on board ships by clarification to remove solids—inparticular abrasive heavy fines removable from the heavy oil bysedimentation or in a centrifugal field and having a given minimumdiameter D (depending on the respective internal combustion engine, forexample: D=10 μm; called catalyst fines or cat fines hereinafter,especially aluminum (compounds) or silicon (compounds), for example Sior SiO₂)—and a removal of an aqueous phase. The proportion of theso-called abrasive catalyst fines in the heavy oil for processing asstarting material in the prior art and also in the process according tothe invention should if at all possible already be below an upper limitof below 60 mg/kg (ppm). Then this content of catalyst fines is to bedistinctly lowered, especially in order that the abrasives do not damagethe diesel engine. According to specifications from diesel constructors,in this regard, even markedly lower upper limits of 20 ppm or even 15ppm or 10 ppm or even 5 ppm should be complied with. This is to beachievable in particular on board ships with a minimum level ofcomplexity.

A known system for processing heavy oil on board ships is shown in FIG.2.

Heavy oil OIL1 which is to be processed and flows in through a conduit101 (here with a valve 102 connected therein) from a tank, which is notshown, and has a starting temperature T0 is first freed of coarse solidsin a soil trap 103 such as a sieve. Then the heavy oil is passed with apump 104 through a heat exchanger 105 in which it is heated to atemperature of up to 98°.

The heated heavy oil is passed out of the heat exchanger 105 through aconduit section 106 into a centrifuge, a three-phase separator 107 here,in which a soil/water phase W is separated from the heavy oil and flowsaway through an outlet 108, and in which it is cleaned to free it of asolid phase S which contains the abrasive catalyst fines and which isremoved via an outlet 109. The processed heavy oil phase—the “cleanoil”—OIL2 is passed out of the separator 107 through an outlet 110 forfurther use. It can be passed here into an intermediate tank (not shownhere) or fed directly to combustion in a diesel engine. The heatexchanger 104 is preferably fed with thermal oil or saturated or hotsteam (also referred to hereinafter as “HS”) as thermal energy-releasingmedium, from which the thermal energy serves to heat the heavy oil incountercurrent.

This method is to be improved further.

Solving this problem is the object of the invention.

The invention achieves this object by a method having the features ofclaim 1 and of the further independent claim 11.

The at least intermittent or permanent increase in the separationtemperature according to claim 1 increases the separation efficiency. Inthis way, lower catalyst fines contents and, at the higher temperaturesof more than 100° C. or more than 105° C. or more than 110° C. or evenmore than 115° C., even lower catalyst fines contents in each case canbe achieved in the clean oil.

An additional particularly advantageous feature is the optional heatingin two stages. Firstly, in this way, the increase in the temperature tothe very high separation temperature need not be effected untilimmediately before the actual separating operation. In addition, themultistage and especially two-stage heating of the heavy oil forprocessing allows the “clean oil” which has been heated to theseparation temperature and conducted out of the at least one centrifuge,especially the (three-phase) separator, to be utilized for flow througha heat exchanger in order to release heat in countercurrent to the “feedfuel” to be cleaned, in order to heat it to a first temperature T1, butone which is still lower than the separation temperature T2. Thisreduces the amount of heat needed overall for heating of the heavy oilto the separation temperature T2, and keeps the clean oil temperature inthe downstream pipelines below the temperature T2 of otherwise possiblymore than 100° C.

The invention of claim 11 additionally achieves optimized closed-loopcontrol of a generic method but also of a method of the invention asclaimed in any of claims 1 to 10.

Thus provided is an advantageous method as claimed in any of thepreceding claims or method for on-ship processing of heavy oil which isto be utilized as fuel for a diesel engine, having the following steps:a) providing heavy oil (OIL1) for processing; b) passing the heavy oil(OIL1) provided and for processing from step a), especially using atleast one pump, onward into a centrifuge, with heating of the heavy oilfor processing before it reaches the centrifuge to a separationtemperature of—preferably—more than 98° C., and c) separating an aqueousphase and a sludge phase from a clean oil phase (OIL2) in thecentrifuge, also with performance of one or more of the following stepsd) to f): d) the catalyst fines content (Cat Fines IN) in the incomingheavy oil for processing—especially prior to heating—is determined witha sensor device, e) the catalyst fines content (Cat Fines OUT) in theoutgoing cleaned or processed clean oil is determined with the or asecond sensor device, f) the catalyst fines content(s) determined fromstep d) and/or e) is/are used as process variable(s) in a closed-loopcontrol process and the process variable(s) determined are used with aclosed-loop control device for closed-loop control especially of theseparation temperature T2 and/or the throughput of the pump.

Preference is given to using the following as process variables:

-   -   current fuel consumption of the engines,    -   current fuel level in a clean oil tank,    -   catalyst fines content in the incoming or outgoing heavy oil        and/or clean oil and/or current service tank overflow rate.

Further advantageous configurations are the subject of the dependentclaims.

The invention is described in more detail by working examples with thefigures which follow. The figures show:

FIG. 1 a plant of the invention for processing heavy oil;

FIG. 2 an already known plant for processing heavy oil;

FIG. 3 a tank arrangement for storing heavy oils; and

FIG. 4 a tank arrangement for storing heavy oils having anoverflow-dependent closed-loop pump control system.

In the plant in FIG. 1, heavy oil OIL1 for processing, which flows inthrough a conduit 1 (here with a valve 2 connected therein) from a tankHT1, is first preferably freed of coarse solids in a soil trap 3 such asa sieve.

Then the heavy oil OIL1 for processing—preferably with the aid of a pump4—is passed from a tank T1 in which it has a starting temperature T0 of,for example, 40° to 60° C. through a first heating device, especially afirst heat exchanger 5A, in which it is heated to a first temperatureT1>T0, higher relative to the starting temperature, of preferably lessthan 95, especially 60° to 80° C.

The heavy oil heated to the first temperature T1 is passed from thefirst heating device, especially the first heat exchanger 5A, through aconduit section 6 into a second heating device, preferably a second heatexchanger 5B, in which it is heated at least intermittently orpermanently to an even higher second temperature T2 compared to thefirst elevated temperature T1. This temperature T2 is greater than 98°C., preferably greater than 100° C., especially greater than 105° C. andpreferably even greater than 110° C. Separation temperatures of up to125° seem advisable at present, particular preference being given to therange between 100° and 115° C., since the apparatus complexity can stillbe controlled efficiently within this range, but, on the other hand,particularly good separation results are achieved in terms of theremoval of catalyst fines.

The heavy oil OIL1 heated to the second temperature T2 is passed out ofthe second heat exchanger 5B directly into at least one centrifuge, herea three-phase separator 7, in which a soil/water phase W is separatedfrom the heavy oil and flows away through an outlet 8, and in which itis cleaned to free it of a solid phase S which is removed via an outlet9. The clarifying to remove solids and the separation of the water phasefrom the oil phase can also be effected in two series-connectedcentrifuges (clarifier and phase separator). According to FIG. 2, inaddition, a process water supply P is provided in the separator 7.

Preferably, the oil takes only a very short time from passing out of the2nd heat exchanger until it enters the centrifuge, in order that it ispassed or passes directly from the second heating device, the secondheat exchanger 5B here, into the centrifuge, a three-phase separator 107here. What is advantageous about this procedure is that the heavy oil,before reaching the centrifuge, cannot lose heat, or cannot do so to anydegree of practical relevance, which would detract from the processingoperation.

The processed heavy oil phase—called OIL2 or synonymously also “cleanoil” hereinafter—is passed out of the separator 7 through the outlet 10for further use.

Preferably, the clean oil, before being introduced into a tank or intoan internal combustion engine, is first used as thermal energy-releasingmedium in the first heat exchanger 5A, i.e. passed through it, in orderto release thermal energy to the incoming heavy oil for processing.

In this way, heavy oil leaving the separator 7 is advantageously used toheat the heavy oil in the first heat exchanger 5A to the firsttemperature T1 and, on the other hand, to cool down the heated cleanoil, such that it is especially storable in a simpler manner. Therecovery of energy distinctly increases the economic viability of theprocessing method, since the energy consumption for heating the heavyoil to the separation temperature is lowered overall. In the second heatexchanger 5B, the thermal energy-releasing medium used may especially besaturated or hot steam HT or another suitable medium, with which it isthen merely necessary to heat the heavy oil from the first temperatureT1 to the second temperature T2.

Until an adequate operating temperature of the heat exchangers isattained, it is possible at first, in the course of startup, also topass heavy oil for processing in circulation for a while through the twoheat exchangers 5A and 5B and then back into the tank T1 (indicated bythe conduit 13 and the two-way valve 14).

It is advantageous, in the incoming heavy oil for processing—for exampleprior to heating—to use a sensor device 11 to take measurements of thecatalyst fines content in the dirty oil for processing coming into theseparator (Cat Fines IN). Preferably, measurements of the catalyst finescontent (Cat Fines IN) are additionally also made in the outgoingcleaned or processed clean oil—for example directly in the clean oilrunning out of the separator—with the same sensor device 11 or with asecond sensor device 12. In this case, the proportion of fines having amean diameter below a limit (especially less than 10 μm) can bedetermined, for example. These measures need not be effected directly inreal time. Instead, it is also possible to take samples (for example atintervals of a few hours in each case) which are then analyzed with asuitable sensor system—as commercially available in principle—for thecatalyst fines content.

The measurements determined are then advantageously passed to a computerunit, not shown here, which is utilized as (closed-loop) control devicefor control of the plant shown in FIG. 1 and which is used forclosed-loop control especially of the separation temperature T1 and/orthe throughput with the pump 4 using the process variables determined.The closed-loop control can be effected as described above or,alternatively, optionally also in real time with online measurements ofthe catalyst fines content.

In this way, the processing method can be controlled precisely.

Closed-loop control variables used may especially be the catalyst finescontent mentioned, which is to be kept below a setpoint value, thecurrent fuel consumption of the internal combustion engine as processvariable and/or the actual level in a clean oil tank.

It is thus possible in a very efficient manner by the process of theinvention, in a simple manner, to adapt the separation efficiency to thecurrent fuel quality (catalyst fines content or “cat fines content” inthe heavy oil for processing according to the defined limit) and to thecurrent mode of engine operation.

A reduction in the throughput increases the separation efficiency. Inaddition, the electrical energy consumption is also reduced when thefeed pump speed is reduced.

It is therefore advantageous to assign a control device, especially afrequency converter, to the pump 4, in order to be able to alter thefeed pump speed in a simple manner, preferably under closed-loopcontrol.

In this way, in a simple manner, the throughput in the processing methodcan be used for closed-loop control as a function of one or more of thefollowing measurement parameters or process variables:

-   -   b) of the current fuel consumption of the engines    -   c) of the current fuel level in a clean oil tank    -   d) of the present catalyst fines content (“cat fines content” in        the clean oil outlet).

The—at least intermittent—increase in the separation temperature to morethan 98° C. described improves the separation efficiency and enables theattainment of very low catalyst fines contents. The proportion ofabrasive catalyst fines can be lowered in a simple manner below limitsdefined by engine manufacturers, which may also be well below 20 ppm oreven below 15 ppm or 10 ppm or lower. With a further increase intemperature, the result of the separating operation is improved further,although the apparatus demands are lower at temperatures up to 115° C.than for even higher temperatures.

It is particularly advantageous to heat the heavy oil, preferably in twoor more stages, to the separation temperature T2 of more than 980,especially more than 100° C. or 105° C. or more, and to undertake theseparating operation at this separation temperature T2. The multitude ofstages increases economic viability further, since it is possible torecover energy. But it is also conceivable to warm or to heat the heavyoil directly to the separation temperature T2 in just a single heatingdevice.

The way in which the method of the invention works is illustrated inmore detail with reference to the results of an illustrative testconducted on board a ship.

This involved making measurements, on board a ship equipped with a plantof the type according to FIG. 2, of the catalyst fines content in theincoming dirty oil for processing running into the separator (Cat FinesIN) and in the clean oil running out of the separator (cat fines OUT):

TABLE 1 Flow Separation Cat fines Cat fines Measurement rate temperature[ppm] [ppm] Efficiency number [L/h] [° C.] IN OUT [%] 1 7800 98 19 11 422 7800 105 21 6 71 3 2000 97 23 7 70 4 2000 110 23 3 90

As can be seen, the measures of the high separation temperature of theheavy oil of more than 100° C., especially more than 103° C., morepreferably 105° C. to 110° C., and, in addition—if necessary andpossible—lowering of the throughput, achieve very good results in termsof low fines or cat fines contents.

FIG. 3 shows a particularly advantageous tank arrangement having severaltanks connected in a particularly advantageous manner to one another andto the plant of FIG. 2. In FIG. 3, the heat exchangers and furtherdetails from FIG. 1 were not included in the drawing to improve clarity.

Two settling tanks ST1, ST2 are provided here, and two service tanksST3, ST4, into which either clean oil OIL2 or else heavy oil OIL1 forprocessing can be introduced as required. The conduit 10 thereforebranches into all these tanks ST1 to ST4.

The tanks ST1 to ST4 also each have at least one outlet. These outletscan each be opened with valves V1 to V4 in the desired manner. All theoutlets also open into the inlet 1 in FIG. 2. This arrangement can bemanaged in a particularly flexible manner and gives options for storageof oils of various quality and also for pre-processing of oils whichhave been stored in the tanks for a long period by first “circulating”the oil from the tanks, then “pre-processing” the oil, for example, at alower temperature up to 98° C., and then passing it back into the sametank.

The working example of FIG. 4 corresponds substantially to that fromFIG. 3, but has been supplemented with an overflow-dependent closed-looppump control system. For this purpose, service tanks ST3 and ST4 have atleast one overflow conduit 201, 202 to the service tanks ST1 and ST2.

These overflow conduits 201, 202 should preferably be disposed in thelower region of the service tanks ST3 and ST4, in order to be able torecycle any possible sediments into the service tanks ST1 and ST2.

Flow indicators FIC are connected within each of the overflow conduits.These are connected to a closed-loop control device 203 which uses theflow rate into the overflow conduits here as the only process variableor as one of the process variables that it advantageously uses as welltakes into account in the closed-loop control of the pump 204.

The throughput of a pump 104 is subject to closed-loop control via aflow indicator 203 connected within the overflow conduits.

1.-12. (canceled)
 13. A method for on-ship processing of heavy oil whichis to be utilized as fuel, comprising the steps of: a) providing theheavy oil for processing; b) passing the heavy oil using a pump into acentrifuge with heating of the heavy oil, at least intermittently orpermanently, to a separation temperature of more than 98° C. before theheavy oil reaches the centrifuge; and c) separating an aqueous phase anda sludge phase from a clean oil phase in the centrifuge.
 14. The methodas claimed in claim 13, wherein one condition for the intermittentheating of the heavy oil to the separation temperature of step b) isthat a content of catalyst fines that is separable in a centrifugalfield exceeds a first upper limit in the heavy oil and/or a second upperlimit in clean oil running out of the centrifuge.
 15. The method asclaimed in claim 13, wherein the heating is effected in a single step.16. The method as claimed in claim 13, wherein the heating is effectedin at least two heating steps.
 17. The method as claimed in claim 16,wherein the heavy oil is passed in a first heating step through a firstheating device wherein the heavy oil is heated to a first temperatureT1, and wherein the heavy oil is then passed in a second heating stepthrough a second heating device wherein the heavy oil is heated to asecond temperature T2 which is higher than the first temperature T1 andwhich is the separation temperature.
 18. The method as claimed in claim13, wherein the heavy oil is passed into the centrifuge immediatelyafter attainment of the separation temperature.
 19. The method asclaimed in claim 13, wherein thermal energy from clean oil running outof the centrifuge is utilized to heat the heavy oil.
 20. The method asclaimed in claim 17, wherein thermal energy from clean oil running outof the centrifuge is released in the first heating device to the heavyoil to heat the heavy oil to the first temperature T1.
 21. The method asclaimed in claim 13, wherein the separation temperature is greater than100° C.
 22. The method as claimed in claim 13, wherein a feed output ofthe pump is adjustable.
 23. A method for on-ship processing of heavy oilwhich is to be utilized as fuel, comprising the steps of: a) providingthe heavy oil for processing; b) passing the heavy oil using a pump intoa centrifuge with heating of the heavy oil to a separation temperatureof more than 98° C. before the heavy oil reaches the centrifuge; c)separating an aqueous phase and a sludge phase from a clean oil phase inthe centrifuge; d) determining a catalyst fines content in the heavy oilwith a first sensor device; e) determining the catalyst fines content inclean oil running out of the centrifuge with a second sensor device; andf) using the catalyst fines content determined in step d) and/or in stepe) as a process variable in a closed-loop control process for theseparation temperature and/or a throughput of the pump.
 24. The methodas claimed in claim 23, wherein the following are used as processvariables in the closed-loop control process: current fuel consumptionof an engine; current fuel level in a clean oil tank; and/or currentservice tank overflow rate.